Radar sensors are utilized, for example, in motor vehicles in conjunction with driver assistance systems, such as adaptive cruise control systems or collision warning systems, and are used to detect the traffic surroundings of the vehicle. In particular, such radar sensors are used to measure the distances and relative velocities of preceding vehicles.
WO 2015/197222 A1 describes a radar sensor, in which a modulation pattern of a transmission signal includes chronologically interleaved sequences of frequency ramps having the same slope and the same deviation. A two-dimensional spectrum is calculated separately for each of the sequences from the obtained base band signals. From a position of a peak in the spectrum, values for the relative velocity of a radar target are determined, which are periodic with a predetermined velocity period. A phase relationship between spectral values, which were obtained at the same respective position in the separately calculated two-dimensional spectra, is checked for agreement with expected phase relationships, which are expected for multiple periodic values of the relative velocity. Based on the check for agreement, an estimated value for the relative velocity of the radar target is selected from the periodic values.
WO 2014/075838 A1 describes a rapid chirps FMCW radar, in which a modulation pattern includes at least two ramps, which differ only by a fixed frequency offset and follow each other in a certain time interval, and in which, based on a phase difference of the intermediate frequency signals for these two ramps, an unambiguous approximate value for the object distance is calculated.